I don't see it particularly as an issue of whether a group is mature enough to handle knowing without metagaming. I would hope most groups are (though obviously some ain't :/ ). The question for me is whether it is fun!

Players can play a whole murder mystery game knowing who the villain is whilst playing their characters as if they didn't. And that could be fun if done in a very self-aware way. But normally things are a lot more exciting if information is hidden. At least that's what works for me.